Step up infection control to help stomp out MRSA
Enhanced surveillance, increased awareness, early detection and
appropriate management are needed to control CA-MRSA.
by Tara Grassia, IDN Staff
Writer, April 2006
CHICAGO - Epidemic strains
of methicillin-resistant Staphylococcus aureus (MRSA) have emerged as
community pathogens among patients without established MRSA risk
factors and are now also affecting patients in health care settings.
This has implications for clinical and public health management of
staph infections, and indicates a need for enhanced surveillance and
strategies focusing on increased awareness, early detection and
appropriate management.
“It certainly is important
that we continue to emphasize infection control strategies for MRSA in
health care settings. Increased prevalence of MRSA in the community
may impact the choice of infection control strategies in health care
settings. This is an area we need to learn more about, but we feel
very strongly that increased MRSA in the community is not a reason to
give up on control of MRSA in health care settings,” said Rachel J.
Gorwitz, MD, MPH, at the 16th Annual Meeting of the Society for
Healthcare Epidemiology of America, held here.
S. aureus resistant to
methicillin and all -lactam
antimicrobial agents were first described in 1961 and were almost
exclusively seen in hospitalized patients and those with significant
health care exposure. However, that situation changed rather
dramatically around the late 1990s, according to Gorwitz, medical
epidemiologist in the division of healthcare quality promotion at the
CDC.
“As MRSA strains that
originated in the community enter health care settings, the
epidemiologic and molecular features of MRSA are evolving, and the
microbiologic characteristics of isolates from patients with
community-associated MRSA (CA-MRSA) and healthcare-associated MRSA
(HA-MRSA) infections are no longer as distinct as they were
initially,” she said.
Initially, many MRSA
experts suspected that community cases of MRSA were the result of
exposure to MRSA in a health care setting. CA-MRSA is
epidemiologically defined as MRSA with onset in the community in a
patient that lacks established MRSA risk factors, such as recent
hospitalization or surgery, long-term care, dialysis, indwelling
catheters and history of previous MRSA infection.
Gorwitz described the
microbiology of MRSA isolates seen in the community, explained the
prevalence of S. aureus infections and suggested various methods to
control MRSA transmission in the community.
Spectrum of S. aureus
“The clinical spectrum of
S. aureus in the community includes asymptomatic colonization, skin
infections and, less commonly, severe and invasive infection,” Gorwitz
said.
A nationally
representative survey, conducted by the CDC, evaluated the prevalence
of nasal colonization with S. aureus in the United States in 2001 and
2002 and found that, overall, the prevalence of S. aureus nasal
colonization was 32.4%. In contrast, the prevalence of MRSA nasal
colonization was 0.8% and was associated with age older than 60 years
and female sex. A follow-up study is being conducted to determine
whether the prevalence of nasal colonization with MRSA has increased.
Community strains may also be more likely to cause disease, but less
likely to cause colonization, according to Gorwitz.
Regardless of the
available data, she stressed that several important questions about
MRSA colonization remain. For one, is MRSA colonization increasing in
the community? According to Gorwitz, some studies suggest it is. Data
by Creech et al, published in Pediatric Infectious Diseases Journal,
showed that among pediatric patients attending health maintenance
visits, MRSA colonization jumped from 0.8% in 2001 to 9.2% in 2004.
Another unanswered
question with limited data is the association between MRSA
colonization and risk for infection compared with methicillin-susceptible
S. aureus (MSSA). A study by Ellis et al, published in Clinical
Infectious Diseases, indicated that risk of S. aureus skin infection
was 38% among soldiers with MRSA colonization compared with 3% in MSSA
colonized soldiers.
The CDC’s Active Bacterial
Core Surveillance (ABCs) program is a population-based surveillance
component of the Emerging Infections Program Network that is designed
to study the incidence and epidemiological features of bacterial
infections and track drug resistance in the nation. Participating
sites identify culture-confirmed cases of MRSA infection in their area
and classify them as CA-MRSA or HA-MRSA.
The first phase of the
study was conducted in 2001 and 2002 in areas of Maryland, Georgia and
Minnesota and phase 2 began in 2004 and expanded to areas of nine
states: California, Colorado, Connecticut, Georgia, Maryland,
Minnesota, New York, Oregon and Tennessee. ABCs total study population
consists of 16.2 million people. The first phase study results,
published by Scott Fridkin and colleagues in The New England Journal
of Medicine, showed that CA-MRSA infections presented most commonly as
skin and soft tissue infections. Of 1,647 patients with CA-MRSA, 77%
had skin or soft-tissue infections, 10% had wound infections, 4% had
urinary tract infections, 4% had sinusitis, 3% had bacteremia and 2%
had pneumonia.
The CDC recently
collaborated with a group called EMERGEncy ID Net, a network of 11
academic emergency medicine departments, on a study to evaluate the
epidemiology of skin infections among adults presenting to emergency
departments. Data by Moran et al, presented at the May 2005 Society
for Academic Emergency Medicine meeting, showed that MRSA was isolated
from 59% of skin infections from which cultures could be obtained.
This prevalence ranged from as low as 15% in New York to as high as
74% in Kansas City. The researchers also determined that MRSA was the
most commonly identified organism in purulent skin infections in all
but one of the participating sites. Among MRSA isolates, 98% carried
genes for the Panton-Valentine leukocidin (PVL) toxin and 97% were
USA300. MSSA was isolated from 17% of skin infections; 42% of
susceptible strain isolates were PVL-positive and 31% were USA300,
according to Gorwitz.
“Severe and invasive
manifestations are less common than skin infections, but do occur, and
include presentations such as necrotizing pneumonia and empyema,
sepsis syndrome, disseminated infection with septic emboli,
musculoskeletal infections (such as pyomyositis and osteomyelitis),
necrotizing fasciitis, purpura fulminans and toxic shocklike
syndrome,” she said.
ABCs data showed that the
incidence of invasive MRSA infections jumped from 19 to 33 per 100,000
in Atlanta and from 40 to 115 per 100,000 in Baltimore over the
three-year period between 2001 and 2004. The proportion of those
invasive MRSA infections due to CA-MRSA also increased from 13% to 17%
in Atlanta and from 7% to 24% in Baltimore.
“Incidence of invasive
MRSA infections and invasive community-associated MRSA infections may
be increasing,” she suggested.
In the 2003-2004 influenza
season, the CDC solicited reports of S. aureus community-acquired
pneumonia following influenza-like illness, according to Gorwitz.
Seventeen cases were reported, 15 of which were MRSA. Of the 10 MRSA
isolates available for research, eight were USA300-0114. The patients’
ages ranged between 8 months and 62 years (mean 21 years), 71% (12)
had no underlying illness and 71% (12) had laboratory-confirmed
influenza. Of the total patient population, 94% (16) were
hospitalized, 81% (13) were admitted to the ICU, eight were intubated
and five patients died.
MRSA management
CA-MRSA outbreaks are
often first detected as clusters of abscesses that are often confused
with spider bites.
Factors that facilitate
CA-MRSA transmission include the five C’s, according to Gorwitz:
crowded living conditions, frequent skin-to-skin contact, compromised
skin surface, contaminated surfaces and shared items and barriers to
maintaining cleanliness. The last “non-C” item associated with
transmission is antimicrobial use.
CA-MRSA outbreaks have
been described among sports participants, inmates, military trainees,
children in day care centers, Native Americans, Alaska Natives and
Pacific Islanders, men who have sex with men and, more recently,
hurricane evacuees in shelters, tattoo recipients, and individuals
living in a rural population with a high prevalence of crystal
methamphetamine use, according to Gorwitz.
The CDC held a MRSA
experts’ meeting to establish reasonable strategies for control and
clinical management of MRSA in the community. A document describing
strategies based on the input from MRSA experts and a thorough review
of available data has recently been posted to the CDC Web site.
The group determined that
although it has not necessarily been the standard of practice, it is
important for clinicians to culture skin infections. This can be
beneficial for monitoring patient management and establishing the
local prevalence of antimicrobial resistance in specific geographical
locations, according to Gorwitz. However, Gorwitz said that molecular
typing or toxin typing should not be used to guide management due to
the lack of data.
In terms of treatment,
incision and drainage should be routine for purulent skin lesions, and
empiric antimicrobial therapy may be needed in some cases. It is also
important to use local data to base treatment because the
susceptibility of S. aureus to methicillin and other agents may vary
geographically, according to Gorwitz. More data from controlled
clinical trials are needed to identify optimal treatment strategies.
“A variety of alternative
agents have been proposed; all have advantages and disadvantages, but
the key point is that more data are needed to identify optimal
treatment,” she said.
Participants in the CDC
experts’ meeting also discussed the role of regimens to eliminate S.
aureus colonization in the control of MRSA in the community. Efficacy
data are not available and the emergence of resistance to agents used
for decolonization is a concern. “However, taking into account that
efficacy data are lacking, meeting participants felt that it may be
reasonable to administer decolonization regimens, after optimizing
basic control strategies, in patients with recurrent infections and in
situations where there is ongoing transmission in a closely associated
cohort, such as a household.” However, appropriate regimens, including
agents and schedules, have not yet been established for decolonization
in community settings.
Patient education is a
critical component for MRSA management and prevention. Physicians
should educate their patients on what they can do to prevent spreading
the infection to others.
“Educating people to
maintain hygiene and maintain a clean environment is important. We
need to utilize the variety of educational resources available,” she
said.
Equally important is
maintenance of adequate follow-up, the group suggested. Researchers
suggested a few public health interventions, such as enhancing MRSA
surveillance, targeting empiric therapy to the pattern of outbreak
strains, educating physicians and patients about wound care and wound
containment, promoting enhanced personal hygiene, limiting sharing of
personal items and, in some situations, excluding patients from
certain activities.
“Various studies are under
way and more are needed to determine the best methods for control and
prevention of MRSA in the community. However, strategies focusing on
increased awareness, early detection and appropriate management,
enhanced hygiene and maintenance of a clean environment appear to have
been successful at limiting transmission,” she concluded.
The CDC’s strategy for
MRSA control is available on the CDC Web site.
For more information:
-
Gorwitz RJ. Community-associated methicillin-resistant
staphylococcus aureus (CA-MRSA). 19-02 Meet-the-consultant 2.
Presented at: 16th Annual Meeting of Society for Healthcare
Epidemiology of America; March 18-21, 2006; Chicago.
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Fridkin SK, Hageman JC, Morrison M, et al. Methicillin-resistant
Staphylococcus aureus disease in three communities. N Eng J Med.
2005;352:1436-1444.
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